One of the world's rarest mammals, the saola was discovered in May 1992 during a joint survey carried out by the Ministry of Forestry of Vietnam and WWF in north-central Vietnam.

This animal can be only found in the Annamite mountains of Vietnam and Laos. All known captive saolas have died, leading to the belief that this species can never live in captivity. The total Saola population is less than 750.

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Mountain gorilla

Mountain gorillas live in forests high in the mountains in central Africa.

Its thick fur helps it survive in a habitat where temperatures often drop below freezing.

But as humans have moved more and more into the gorillas' territory, it has been pushed farther up into the mountains for longer periods and forced to endure dangerous and sometimes deadly conditions, WWF said.

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Leatherback turtle

Being the largest sea turtle species and also one of the most migratory, leatherback turtle lives in both the Atlantic and Pacific Oceans.

The numbers of leatherback turtles has seriously declined during the last century as a result of intense egg collection and fisheries bycatch, WWF said.

There are just 35 Javan rhinos in Ujung Kulon National Park at the western tip of Java in Indonesia.

The main factor behind their continued has been poaching for horns - a problem that affects all rhino species.

Loss of habitat because of agriculture has also contributed to its decline, though this is no longer as significant a factor because these rhinos only live in one nationally protected park.

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South China tiger

The South China tiger population was estimated at 4,000 individuals in the early 1950s. Over the next few decades, thousands were killed as the subspecies was hunted as a pest, WWF said.

The NGO Save China's Tigers, with the support of China's State Forestry Administration has developed a plan to reintroduce captive-born tigers into large enclosures in southern China. The main concerns regarding the reintroduction are the availability of suitable habitat and adequate prey.

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Sumatran elephant

Native to the eponymous Indonesia island, the Sumatran elephant is threatened by habitat loss, degradation and fragmentation, and poaching.

In 2004, the Tesso Nilo National Park has been established in Riau Province to protect the Sumatran elephant's habitat. This forest is one of the last areas large enough to support a viable population of elephants.